CN102020651A discloses 6-arylaminopyridonecarboxamide compound represented by formula I as a MEK inhibitor, and a method for treating a MEK-mediated conditions or disorders in a mammal (including a human), such as inflammatory diseases, infections, autoimmune diseases, stroke, ischemia, non-cancer hyperproliferative diseases, tumors, and other diseases.

CN102020651A further discloses a method for preparing a compound of formula I by using a carbodiimide compound as a starting material, such as a preparation method of 6-(2-chloro-4-iodophenylamino)-N-(2-hydroxyethoxy)-5-methyl-4-oxo-4,5-dihydrofuro[3,2-c]pyridine-7-carboxamide as shown in scheme 1,

In this scheme, carbodiimide is very easy to absorb moisture to form urea, and accordingly it is difficult to store. There are extremely strict requirements for the storage environment of reaction raw materials during the scale-up production, thereby increasing the production costs. Furthermore, after absorbing moisture, carbodiimide would introduce impurities into the reaction, and the reaction product needs to be purified to remove these impurities, thereby decreasing the yield and increasing the production costs. In addition, this synthesis route needs the use of sodium hydride. Sodium hydride easily causes burning and explosion, is irritating to the human body, and easy to cause skin burns, and consequently, there is a greater potential safety hazard during the scale-up production. Moreover, sodium hydride causes great damage to the environment, and is not conducive to large-scale production.
Therefore, there is a need to find a new preparation method suitable for the industrial production of an intermediate of a compound of formula I.